There are mainly two ways for producing high electron mobility transistors with isolation structure in conventional technique. One is the mesa etching, by etching the device non-active regions to fabricate the isolation structure; the other is ion implantation, by implanting ion beam into the device non-active regions to produce the isolation structure. The disadvantage of the mesa etching is that the mesa sidewall of the device active regions may lead to increasing the leakage current and also reducing the breakdown voltage. The deeper the mesa sidewall is, the more significant the leakage current is. This greatly influences on the performance of the high electron mobility transistors. Compared with the mesa etching for producing high electron mobility transistors with isolation structure, the ion implantation method saves lots of time and costs of the etching processes and the ion implanted isolation structure may reduce the leakage current problem, and in addition lower the minimum noise figure. However ion implantation isolation structure may be achieved by different types of ion beam. Usually the ion implantation isolation structure is fabricated under high temperature environment because of the physical properties of the ions the conventional technique used. For example, to produce nitrogen ion implantation isolation structure, the temperature usually needs to be around 250° C. to 300° C. During the ion implantation processes or some other processes after ion implantation processes, the implanted nitrogen ions may be activated and the isolation may be reordering because of the temperature during these processes. Hence, this will affect the electrical isolation and lead to increasing the leakage current. Accordingly, the inventor has developed a new design of the method to produce the high electron mobility transistors with isolation structure to solve the above problems. Using the new method, the ion implantation isolation structure may be produced under room temperature, the phenomenon of activation caused by high temperature may be reduced and high electrical isolation with high repeatability and high reproducibility may be preserved.